Urbanization surrounding military training areas worldwide is changing the context and parameters of military training and the military utilization of land set aside for training. The United States and NATO militaries, when deploying, set up training areas. Due to the danger of ricochet and other anomalies, military forces are required to establish “Surface Danger Zones” (SDZs) adjacent military training ranges. The necessity to establish buffers alongside firing ranges requires militaries, or their host nations, to lease, purchase or otherwise acquire large tracks of land and erect warning signs and restrict traffic in these training areas. The maximum range of a projectile determines the size of the area to be set aside as a Surface Danger Zone (SDZ). The Surface Danger Zones (SDZs) are calculated based on the maximum range of the ammunition type(s) used in training along with a myriad of other considerations that include the ricochet danger inherent in the ammunition design. In many cases, militaries also desire to convert existing ranges from one ammunition type to another (for example to re-purpose 0.50 cal ranges to allow for live fire training on medium caliber 25 mm ammunition). In this context, “Short Range Training Projectiles” (SRTP's), also known as “Short Range Training Ammunition” (SRTA), provide both direct and indirect benefits to militaries.
The following U.S. patents disclose different types of Short Range Training Projectiles (SRTPs): U.S. Pat. No. 4,128,060 to Gawlick; U.S. Pat. No. 4,140,061 to Campoli; U.S. Pat. No. 4,911,080 to Leeker and U.S. Pat. No. 5,001,986 to Meister. All of these patents describe methods for modifying air-flow over the projectile body, thereby shortening the projectile's flight path. In addition, European Patent Pub. No. 0,036,232 A1 to DeBrant discloses designs for SRTPs where the outer surface undergoes changes after set-back that induce an aero-ballistic drag that shortens the flight path of the ammunition.
Most of these disclosed methodologies induce a linear increase in aero-ballistic drag and yaw after barrel exit. The introduction of linear aerodynamic forces will increase the drag and reduce the rate of spin of the projectile. In many cases, currently available SRTPs rely on the customer accepting a very loose or inexact ballistic match definition. SRTP designs, as advertised by GDOTS (Canada), CBC (Brazil) and NAMMO (Scandinavia), have external de-spinning features on the ammunition's outer surface where the ammunition induces an immediate reduction in spin and increased drag after barrel exit. The requirement to utilize de-spinning features where the projectile's outer-diameter is modified can, in certain calibers, negatively affect ammunition feeding.